The present invention relates to a storage control technology of electronic files.
For example, a NAS (Network Attached Storage) node (for example, a file server) manages the file, and the body of the file is stored in a storage device inside the NAS node or outside the NAS node.
Generally the files with different names are stored in a storage device even if the file contents is the same. In this case, the files with absolutely identical contents (that is, the files with completely duplicate contents) are stored in the storage device. Therefore, the storage capacity is unnecessarily consumed. The technologies disclosed in Japanese Patent Applications Laid-open No. 2005-235171 and 2005-174339 are examples of storage control technologies for preventing the storage of duplicate files. For example, the following is disclosed in Japanese Patent Applications Laid-open No. 2005-235171 and 2005-174339.
There are present a host and a storage device. The host has an application and a special API (Application Program Interface). The storage device communicates with the special API. When the API of the host receives a file storage request from the application, if the association of the file name of the file and the below-described contents address is not managed, the file is transmitted to the storage device, but if the association is managed, the contents address of the file is transmitted to the storage device. When the storage device receives the file from the API of the host, a hash value is generated from the file contents. This hash value is the contents address. The storage device stores the received file, performs management by associating the generated contents address with the physical storage location of the file, and returns the contents address to the API of the host. The API of the host performs management by associating the contents address received from the storage device with the file name of the transmitted file. On the other hand, when the storage device receives the contents address from the API of the host, the storage device acquires the file from the physical storage location associated with the contents address and returns the acquired file to the API of the host.
With the technology disclosed in Japanese Patent Applications Laid-open No. 2005-235171 and 2005-174339, a hash value generated in the storage device is used as a contents address. Therefore, a special API of a high-level device such as a host is necessary to designate the file with the contents address to the storage device.